Contributed on October 7, 2011

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Marlon Dumas @ BPMN 2010

Transcript

Unraveling Unstructured Process Models
Marlon Dumas
University of Tartu, Estonia
Joint work with Artem Polyvyanyy and Luciano García-Bañuelos
Invited Talk, BPMN’2010 Workshop, Potsdam, 14 Oct. 2010
Poll: Which desk do you
prefer?
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Poll: Which model do you prefer?
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The Problem
•  Premise: Structured is “better”
–  Easier to understand
–  Easier to analyze
–  Easier to automatically layout
–  Easier to abstract (zoom-out)
•  We know not all models can be structured…
•  Which ones can, which ones can’t?
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Analysis of Structured Models
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CTparallel = Max{T1, T2,…, TM}
CT = p1T1+p2T2+…+pmTm=
CT = T/(1-r)
CT = T1+T2+…+ Tm
Laguna & Marklund (2005): Business Process Modeling, Simulation and Design
Automated Layout and Abstraction
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Wil van der Aalst et al., Process Mining Tutorial
A Bit of History
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1968 1969 1970s (and 80s)
20 years (and 200 papers) later…
•  Everything can be structured if you accept to
break and continue
•  Everyone forgot to release their implementation
(they were ashamed since it was full of GOTOs)
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40 years (and 400 papers) later
•  We can structure any BPMN
diagram, except:
–  “Incorrect” ones
–  Cycles with multiple exit points
–  Z-structures
–  Inclusive join gateways, complex
gateways and other demons
•  Try it out: http://sep.cs.ut.ee/Main/bpstruct
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Corollary (if you care)
•  Any (sound) BPMN model can be
transformed into an equivalent (readable)
BPEL process definition
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•  If BPEL had break/continue statements or we use boolean variables to simulate break/continue statememts
•  And the BPMN model does not have inclusive join gateways, complex gateways and other demons
•  And some other minor details not worth mentioning
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Behavioral Equivalence
Preserves the level of concurrency in
a process model
Sequential simulation of a
process model
Fully concurrent
bisimilar (FCB)
Weakly
bisimilar
Weakly
bisimilar
Sequential simulation of a
process model
Starting Point – Process
Structure Tree
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Johnson et al. (PLDI’1994), Vanhatalo et al. (BPM’2008)
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Taxonomy of Process Fragments
■  Trivials, polygons, and bonds are structured fragments
■  Rigids are “unstructured”
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Homogeneous XOR Rigid
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Homogeneous AND Rigid
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Block-structured version…
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Homogeneous AND Rigid that
cannot be structured
•  Causal rules:
–  {A, B}  { C }
–  { B }  { D }
•  Overlap on the left-hand side of the rules
Compare to this…
•  Causal relations
–  {A, B}  {C, D}
Heterogeneous Acyclic Rigid
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Equivalent Structured Fragment
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The Key Ingredient: Unfoldings
An unfolding is a
representation of a net without
“merge” points
A complete prefix unfolding is
a finite initial part of the unfolding
that contains full information
about the reachable states
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Ordering Relations
■ Two transitions of an occurrence net are in one of the following relations:
□  A and B are in causal relation (A>B), iff there exists a path from A to B
□  A and B are in conflict (A#B), iff there are two transitions t1, t2 that share
an input place and there is a path from t1 to A and a path from t2 to B
□  A and B are in concurrency (A||B) relation iff A and B are neither in
causal, nor in conflict relation
A>C1
B>D2
B#A
A#D2
C2||D2
D2||C2
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FCB and Ordering Relations
Two process models are FCB-equivalent …
… if and only if, (complete prefix) unfoldings of both models expose
same ordering relations
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Structuring Process Models
Compute ordering relations
of the (unstructured)
process model
Construct a block-structured
process model from ordering
relations
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Ordering Relations Graph
An ordering relations graph
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Modular Decomposition Tree (MDT)
  The MDT is unique and can be computed in linear time
The MDT
■  A linear (L) module is a total order on a set of nodes of a graph
■  A complete (C) module is a complete graph, or a clique
■  A primitive (P) module is neither trivial, nor linear, nor complete
  A module is a set of edges with uniform structure
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Structuring Acyclic Process Models
A primitive module
Let G be an ordering relations graph. The MDT of G has no primitive module,
iff there exists a well-structured process model W such that G is the ordering
relations graph of W.
Heterogeneous Cyclic Rigid
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For further details…
Download and try:
•  http://sep.cs.ut.ee/Main/bpstruct
•  http://code.google.com/p/bpstruct/
Perspectives:
•  Analyze
•  Decompose (e.g. for distributed execution)
•  Refactor (extract duplicate fragments into subprocesses)
•  Visualize
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